The invention relates to a four-joint wiper arm for a windshield wiper system of a motor vehicle, with one joint formed between a primary shaft and a primary connecting rod, an additional joint formed between the primary lever and a coupling link, an additional joint formed between the coupling link and a supporting rod and an additional joint formed between the control lever and a supporting arbor.
Four-joint wiper arms of this type, for which the curved wiping movement of the wiper blade on the windshield is combined with an additional lifting movement in the longitudinal direction of the wiper blade, are known, e.g., from DE 4,214,679 A1 or EP 0,537,059 A1. In both cases, both the primary lever as well as the control lever are connected to the coupling link by means of a respective one arbor, with both arbors running parallel to each other and perpendicular to the pendulum plane of the coupling link. It is known that the wiper blade must be pressed against the windshield to be wiped with a force great enough to achieve a good wiping quality. The pressure force of the wiper blade is produced by means of a prestressed tension spring, the ends of which are secured to the wiper rod or joint section, on one hand, and to the coupling link, on the other hand, in such a way that the joint section with wiper arm, which is sealed on the coupling link so as to pivot, is moved relative to the coupling link in the direction of the windshield.
Upon contact of the wiper blade against the windshield, a tension produced by spring tension force is transmitted by the pivot bearing between joint section and coupling link into the four-joint assembly. This leads to distortion between the parts of the four-joint assembly, especially in the four pivot bearings. This stress leads, in turn, to an obstruction of the wiping movement, lessening the wiped quality. Distortion in the four-joint assembly also occurs, more specifically, if the four aforementioned joint locations are not mutually aligned with sufficient precision, which can be caused by manufacturing tolerances alone.